Normally when you hitch you want the trailer to ride up on the plate to ensure you don't have a high hook. The force is straight back onto the trailers tires. If you try that from an angle, the trailer legs act to hold the trailer still while you couple. You need to have your pin height at exactly the height of your hitch so you don't lift the trailer off its landing gear, causing it to slide away from the truck and land sideways on the landing gear or end up with a high hook. It can be done but you need to be really careful.